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2010-12-02 00:54:11
Chapter four injury

Radiation injury
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  1. the study of the effects of ionizing radiation on living tissue
    radiation biology
  2. T or F. in diagnostic radiography, not all x-rays pass through the patient and reach the dental x-ray film; some are absorbed by patient tissues
  3. the total transfer of energy from the x ray photon to the pt tissues
  4. what happens when x-ray energy is absorbed by pt tissues?
    chemical changes occur that result in biologic damage
  5. What are 2 specific mechanisms of radiation injury?
    • ionization
    • free radical formation
  6. x-rays are a form of________ radiation, when x rays strike patients tissues,_______results
    • ionizing
    • ionization
  7. what is produced throught he photoelectric effect, or compton scatter, and results in the formation of a positive atom and a dislodged negative electron?
  8. forms a positive atom and a dislodged negative electron
  9. Ionization caus____ ______in the cell that results in biological damage
    chemical changes
  10. Ionization causes chemical changes in the cell that results in ____ _______
    biological damage
  11. X radiation causes cell damage primarily through formation in which type of radiation injury?
    free radical formation
  12. occurs when an x ray photon ionizes water
    free radical formation
  13. What is the primary component of living cells?
  14. Ionization of water results in the production of_____ and____ _____ ____
    • hydrogen
    • hydroxyl free radicals
  15. an uncharged (neutral) atom or molecule that exists with a single, unpaired electron in its outermost shell
    free radical
  16. true or false. a free radical is highly reactive and unstable
  17. What are 3 ways that free radicals can achieve stability?
    • recombine without changes in the molecule
    • combine with ordinary molecules and form a toxin (hydrogen peroxide) capable of producing widespread cellular changes
    • combine with other free radicals and cause change
  18. What toxin s formed when a free radical combines with ordinary molecules and forms a toxin?
    hydrogen peroxide
  19. Damage to living tissues due to exposure to ionizing radiation may result from what 2 things?
    • direct hit and absorption of an x-ray photon within a cell
    • absorption of an x-ray photon by water within a cell accompanied by free radical formation
  20. What are the 2 theories about how radiation damages bioligic tissues?
    • direct
    • indirect
  21. suggests that cell damage results when ionizing radiation directly hits critical areas whtin the cell
    direct theory
  22. What is an example of a critical area in the cell in the direct theory?
  23. Do direct injuries from exposure toionizing radiation occur frequently or infrequently?
    infrequently, most x ray photons pass through the cell and cause little or no damage
  24. suggests the x-ray photons are absorbed within the cell and cause the formation of toxins, which in turn damage the cell
    indirect theory
  25. when x-ray photons are absorbed by water within a cell ___ ____ _______ results
    • free
    • radical
    • formation
  26. In the indirect theory the free radicals combine to form_____ which cause cellular dysfunction and_______ _______
    • toxins (H2O2)
    • biologic damage
  27. an indirect injury results because the _____ ______ combine and form ______
    • free radicals
    • toxins
  28. Why is the chance of free radical formation and indirect injury treat?
    because cells are composed of 70-80% water
  29. used to correlate the 'response' or damage, of tissues with the 'dose' or amount, of radiation recieved
    dose-response curve
  30. When dose and damage are plotted on a graph, a______, ________ relationship is seen
    • linear
    • nonthreshold
  31. indicates tat the response of the tissues is directly proportional to the dose
  32. indicates that a threshold dose level for damage does not exist, suggests that no matter how small the amount of radiation recieved, some damage occurs
  33. Is there a safe amount of radiation exposure?
  34. Biologic effects from radiation can be classified as what 2 types?
    • stochastic
    • nonstochastic
  35. ______ effects occur as a direct function of dose
  36. In what effect does the probability of occurrence increase with increasing absorbed dose; however, the severity of effects does not depend on the magnitude of the absorbed dose?
    stochastic effect
  37. true or false. stochastic effects do not have a dose threshold
  38. What are 2 examples of stochastic effects?
    • cancer (tumor) induction
    • genetic mutations
  39. What is another name for nonstochastic effects?
    deterministic effects
  40. somatic effects that have a threshold and increase in severity with increasing absorbed dose
    nonstochastic (deterministic) effects
  41. What are 4 examples of nonstochastic effects?
    • erythema
    • loss of hair
    • cataract formation
    • decreased fertility
  42. Which biologic effect requires more radiation doses to seriously impair health?
  43. chemical reactions (ionization, free radical formation) that follow the absorption of radiation occur rapidly at the______ _______
    molecular level
  44. varying amounts of time are required for chemical reaction (ionization, free radical formation) changes to alter____ and _____ _______
    • cells
    • cellular functions
  45. true or false. the observable effects of radiation are not visible immediately after exposure
  46. the time that elapses between exposure to ionizing radiation and the appearance of observable clinical signs
    latent period
  47. The latent period may be short or long depending on what 2 things?
    • total dose of radiation recieved
    • amount of time, or rate it took to recieve the dose
  48. The more radiation recieved, and the faster the dose rate, the_________the latent period
  49. cell death, changes in cell function, breaking or clumping of chromosomes, formation of giant cells, cessateion of mitotic activity, or abnormal mitotic activity are all examples of what?
    period of injury
  50. What is the last event in the sequence of radiation injury?
    recovery period
  51. What is the order of the radiatio injury sequence?
    latent period - period of injury - recovery period
  52. true or false. all cellular radiation injuries are permanent
  53. with each radiation exposure, cellulear damage is followed by____
  54. Most of the damage caused by _______ radiation is repaired with cells of the body.
  55. effects of radiaion exposure are additive and damage that remains unrepaired accumulates in the tissues, is termed:
    cumulateive effects
  56. ____________ of repeated radiation exposure can lead to health problems.
    cumulative effects
  57. Radiation effect on hematopoietic (blood forming):
  58. radiation effects on reprocuctive (ova, sperm)
  59. radiation effects on thyroid
  60. radiation effects on skin
  61. radiation effects on eyes
  62. Name 5 factors that influence radiation injury:
    • total dose
    • dose rate
    • amount of tissue irradiated
    • cell sensitivity
    • age
  63. the quantity of radiation received, or the total amount of radiation energy absorbed
    total dose
  64. the rate at which exposure to radiation occurs and absorption takes place
    dose rate
  65. dose rate = _______
  66. Why does more radiation damage take place with high dose rates?
    because a rapid delivery o radiation does not allow time for the cellular damage to be repaired
  67. the areoas of the body exposed to radiation
    amount of tissue irradiated
  68. What is an example of total body irradiation?
    a person exposed to a nuclear energy disaster
  69. extensive radiation injury occurs when large areas of the body are exposed because of the damage that occurs to the______ _________ _________
    blood forming tissues
  70. true or false. cell sensitivity affects radiation injury
  71. are children or adults more susceptible to radiation damage?